Help needed on how to remove PCIe graphics card.(retention clip)

Hi, im just days away from purchasing a new 8800GT to upgrade my current E520's graphic card. Problem is, my dad decided to buy the graphics card and bring it back home- which means i have to take the old one out and put the new 8800Gt by myself. Thing is, I have completely no idea on how to remove the graphics card from its slot. As from what i heard, the PCIe x16 slot has some kind of retention clip to prevent the card from getting loose. Furthermore, i've read about people spoiling the slot and the graphics card itself for not releasing the retention clip. I've read online guides but i still have doubts. Any help and advice would be greatly appreciated. Thanks in advance.